A pupil of the Dao ethnic tribe returns home from school along a hillside path at Suoi Thau village in Hoang Su Phi district of Vietnam's northern province of Ha Giang, located at the border with China, September 18, 2015. (Photo by Reuters/Kham)

Sports Finalist – Ian MacNicol. Michalina Kwasniewska of Poland competes in the Women's high jump during day one of The European Athletics U23 Championships 2013 on July 11, 2013 in Tampere, Finland. (Photo by Ian MacNicol/Agence France-Presse)

A file photograph dated 07 January 2006 and released by Greenpeace, showing the Yushin Maru, a factory ship in a Japanese whaling fleet, injuring a whale with it's first harpoon attempt. A UN court in The Hague on 31 March 2014 halted Japan's much-criticized whaling programme, ruling that it contravenes a 1986 moratorium on whale hunting. Japan must end its 'research whaling' programme, the International Court of Justice (ICJ) said. Japan said the programme was for scientific research and permitted under international conventions. Australia had brought the case to the ICJ in 2010, charging that Japan was breaching international law by killing hundreds of whales every year for commercial purposes. Japan was “deeply disappointed” by the ruling, an unnamed government official was quoted by the Kyodo News agency as saying. But the official said Japan would stand by the ruling. (Photo by Kate Davison/EPA)

Photographer Lori Nix hand-crafted dioramas are fictional scenes of a post-apocalyptic world in which plants and decay reclaim both grand and mundane structures. Each structure is built in Nix's living room and can take over half a year to build. Photo: Library, 2007. Photographer Lori Nix says this is the most popular image she has made for this project that she calls “The City”. (Photo by Lori Nix)

A rainbow is seen near a cloud south of Corvallis, Ore., Monday, May 19, 2014. (Photo by Andy Cripe/AP Photo/The Corvallis Gazette-Times)

Throughout the course of the long war in Afghanistan, Coalition troops have relied on thousands of military working dogs to help keep them safe, and make their jobs easier. The dogs are trained to detect explosives, to find illegal drugs, to search for missing comrades, or target enemy combatants. Not only are they active on the front lines, but behind the lines they serve as therapy dogs, service dogs, and loyal companions. They also share the same risks as the ground troops, suffering injuries and sometimes death on the battlefields. Gathered here are images of these dogs and their handlers in Afghanistan and back home, from over the past several years, part of the ongoing series here on Afghanistan.

Visitors wear shirts with an image of former Chinese leader Mao Zedong at the Shanghai World Expo site in Shanghai, May 2, 2010. (Photo by Aly Song/Reuters)

Russian servicemen drive a partially covered T-14 Armata tank along a street before a rehearsal for the Victory Day parade in Moscow, Russia, April 29, 2015. Russia will celebrate the 70th anniversary of the victory over Nazi Germany in World War Two on May 9. (Photo by Maxim Zmeyev/Reuters)